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INVENTOR. WLLAM R. SOAN

ATTORNEYS 3,069,681 United States Patent Office Patented Dec. 18, 1962 2 3,069,681 when the electrodes are respectively pulsed. Each of the SYSTEM FOR LARGE-AREA DISPLAY OF pluralities of electrodes is in spaced-apart alignment along TWO,-COLOR ENSFORMATION one dimension of the sheet and the two pluralities of William R. Sloan, Fort Wayne, Ind., assignor to Inter electrodes are respectively spaced-apart along the other national Telephone and Telegraph Corporation dimension of the sheet. Means are provided for moving Filed Mar. 14, 1960, Ser. No. 14,743 the sheet with respect to the electrodes along the other 9 Claims. (Cl, 346-74) dimension. First switching means is provided sequen tially coupling the first electrodes to the converting means This invention relates to a system for presenting in for sampling one of the color-responsive signals at dis two colors alpha-numeric information, i.e., words and Crete intervals and for pulsing the first electrodes respon numbers, and graphical information, such as maps, sive to the presence of the one color signal at the respec graphs, etc., visually on a large-area display for group tive intervals. Second switching means is provided viewing. sequentially coupling the second electrodes to the con There are occasions when it is desirable visually to Verting means for sampling the other of the color display various types of printed and/or graphical infor responsive signals at discrete intervals and for pulsing mation on a large-area surface to permit viewing thereof the second electrodes responsive to the presence of the by a number of persons, and it may further be desirable other color signal at the respective intervals. First and to display Such information in two separate colors, e.g., Second means for applying charged toner material of two black and red. In the past, such large-area displays have different colors respectively are provided, one color being been provided by conventional optical projection tech 20 applied to one side of the sheet and the other color niques which generally required a darkened room for being applied to the other side of the sheet. Thus, the optimum viewing and further involved substantial power first sequential switching means and its associated toner requirements. Furthermore, in instances where the alpha applying means may form black dots on the outer sur numeric or graphical information to be displayed is in face of the dielectric sheet while the second sequential the form of coded electrical characteristics, optical pro 25 switching means and its associated toner applying means jection requires the intermediate step of printing the may form red dots on the inner surface of the sheet. information before it can be optically projected, and like The red toner material applied to the inner surface of wise, graphical information conventionaily requires trans the sheet will, of course, adhere to the incremental fer to a transparency for best optimum projection. charged areas formed by the first switching means; how In application Serial Number 18,008, filed March 28, 30 ever, they will be masked by the opaque black toner 1960 of Eugene S. Hawkins, which is assigned to the material previously applied to these incremental areas assignee of the present application, there is described a on the outer surface of the sheet, Thus, the rod dots system for large area display of alpha-numeric and formed on the inner surface of the sheet will be visible graphical information which does not employ optical for viewing through the transparent sheet only in those projection techniques. In accordance with the invention 35 areas where incremental charges were not formed by the of that application, a printed page or a rectangular graph first switching means and first electrodes. ical display is divided into a matrix comprising a pre The above-mentioned and other features and objects determined number of discrete dots, the number depend of this invention and the manner of attaining them will ing upon the resolution required, e.g., much in the nature become more apparent and the invention itself will be of a newspaper half-tone. Thus, the area to be viewed 40 best understood by reference to the following description is divided into incremental areas, such as 1,000 dots of an embodiment of the invention taken in conjunction horizontally and 1,000 dots vertically to provide a poten with the accompanying drawings, wherein: tial of 1,000,000 dots. In order to display the infor F.G. 1 is a schematic illustration in block diagram mation in dot form, the horizontal dimension of the form showing the fundamentals of my invention; display surface is divided into a number of discrete FIG. 2 is a side-elevational view of the display means incremental segments and one horizontal line of the 45 of FIG. 1; alpha-numeric or graphical information is formed by FIG. 3 is a block diagram illustrating one embodiment sequentially scanning the line and forming dots where of my invention for presenting alpha-numeric information marks are required. Thus, the horizontal dot-forming in two colors, and mechanism and the display surface are moved vertically 50 FIG. 4 is a schematic illustration showing the preferred with reference to each other as scanning is repeated to embodiment of the dot- employed in FIGS. 1 form a rectangular display, much in the nature of a and 3. raster. In the preferred embodiment of the Referring now to FIGS. 1 and 2 in which the broader above-referred to Hawkins' application, the display sur aspects of my invention are illustrated, my improved sys face is in the form of an endless belt of dielectric mate 55 ten for large-area display of alpha-numeric and graphical rial and the dots are formed by well known xerographic information, generally identified at 10 comprises converter techniques. 12 which receives the alpha-numeric or graphical in The system described and illustrated in the aforemen formation and converts the same into a first time-based tioned Hawkins' application displays information in only electrical signal having characteristics respectively respon one color, and therefore it is an object of my present 60 sive to the information in the two colors. If alpha invention to provide a system of the general type dis numeric information is to be displayed, the input informa closed in the Hawkins' application for displaying infor tion may be in digital form, i.e., a pulse code from a mation in two colors. or teletype coded as to character, position and In accordance with the broader aspects of my inven color. Converter 12 would then include means for tion, therefore, I provide means for receiving information decoding the digital input to identify the particular char and for converting the same into two time-based signals 65 acters, their respective locations on the page to be respectively responsive to the information in the two displayed, and their respective colors. Converter 12 will colors. The display surface is in the form of a rela also include a character generating device, such as a tively, thin sheet of transparent dielectric material and tube, for providing a time-based video signal means including first and second pluralities of electrodes corresponding to the input character. Since the input rate are provided cooperating with the dielectric material sheet 70 of the System 10 may be considerably faster than the to form incremental electrostatic charges in dot form printing rate, it will also be desirable to provide storage 3,069,681 3 4. means in converter 12 to store the character-responsive The first color toner applicator 66 is provided spaced signals for subsequent reading-out at a “slower speed con from printing heads 36 in the direction of movement 34 sistent with the capabilities of the printing apparatus. of belt 22 and is arranged to apply a first color charged The signals may be stored in the storage means at two toner, for example black, on the outer surface of dielectric different levels responsive to the two different input colors, 5 belt 22. A second color toner applicator 63 is spaced and likewise subsequently read-out at two different levels. from printing heads 33 in the direction of movement 34 Graphical information may also be in coded digital form, of belt 22 and is arranged to apply a second color charge or may be fed directly into the system in the form of toner, for example red, on the inner surface of the dielec X-Y voltages at levels corresponding to the two colors. tric belt 22; it will be observeci that the first color toner The first time based signal provided by the converter 10 is applied to the outer surface of run 28 of belt 22 whereas 12 is fed to a signal separating circuit 14 which separates the Second color toner is applied to the inner surface of the first time-based signal into two time-based signals run 38 of belt 22 so that it is not required to make contact respectively corresponding to the two color characteristics with the rollier 24. The area 70 of run 32 of belt 22 forms in the first time-based signal. Thus, if the first time-based the viewing area, and an opaque shield 72 is provided signal provided by converter 2 has two different levels 5 Spaced from the inner surface of area 78 of belt 22 in corresponding respectively to the two-color input informa order to enhance the viewing characteristics. tion, signal separator 4 may comprise two clipping cir The signal converter 12 provides the first time-based cuits which respectively clip the first time-based signal to output signal in raster form, i.e., having both a horizontal provide in output circuits 6 and 18 first and second time and vertical time-based characteristic. To provide the based color signals, respectively corresponding to the two 20 horizontal and vertical time-based characteristic in the color information. first time-based signal provided by converter 12, horizon The large-area display means 20 of my invention com tal and vertical Sweep generators 74 and 76 are provided prises an endless belt 22 formed of relatively thin trans respectively coupled to the converter 12. Horizontal parent dielectric material, such as Mylar, which is trained Sweep generator 74 is coupled to pulse generator 60 and around rollers 24 and 26 to provide parallel runs 28 and 25 Synchronized thereby so that a new horizontal sweep of 30, as shown. The lower roller 24 may be driven by converter 2 is initiated responsive to the completion of synchronous drive motor 32 thus to move the belt 22 in One complete Sequential connection of electrodes 40 of the direction shown by the arrows 34. Scanning head 36 to battery 56. Likewise, vertical sweep In order to “print” the information on dielectric belt 22 generator 76 is coupled to vertical drive motor 32 and in the desired two colors, I provide first and second color 30 Synchronized thereby, thereby to synchronize the vertical printing heads 36 and 38 respectively cooperating with Sweep of converter 12 with the vertical movement of the the two runs 28 and 30 of belt 22. The printing heads belt 22. 36 and 38 extend transversely across belt 22, i.e., trans Assuming now that the first time-based signal during the verse with respect to the direction of movement 34 of first one-half of the first horizontal scan thereof is calling the belt. In the simplest form, shown in FIG. 1, each 35 for black information, which may be a Component of the of the printing heads 36 and 38 comprises a plurality of black "E" shown at 78 on belt 22, only the first color incremental charge-forming electrodes 4 in spaced apart signal Will be present in the first output circuit 16 of sig alignment and respectively spaced from the outer surface nal Separator 14 and there will be no output signal in the of belt 22 and another electrode 42 on the inner surface output circuit 18. Thus, during this period, gate 52 will of the belt 22 and spaced therefrom, cooperating with 40 be open responsive to the presence of the first color signal the plurality of electrodes 40. in output circuit 16 of signal separator 14 and therefore First and second color dot switches 44 and 46 are pro Sequential connection of the first five dot-forming elec vided respectively comprising first and second color se trodes 46 of printing head 35 to battery 56 will result in quential switching devices 48 and 53 and gate devices 52 the formation of a horizontal row of five incrementally and 54. Switching devices 43 and 50 sequentially con charged areas in dot form, which, after the belt passes the nect the respective dot-forming electrodes 40 to a suitable black toner applicator 66 will have black toner material source of positive potential, shown here as batteries 56 adhered thereto forming the row of dots 88. Proceeding, and 58, while gates 52 and 54, when actuated, connect the it is now assumed that after a brief interval in which no respective electrodes 42 to ground, as shown. information is provided in the first time-based signa? pro Sequential switching devices 48 and 50 are actuated by 50 vided by converter 2, the signal now calls for ared out pulses provided by pulse generator 66, the pulse generator put. Thus, there will be no first color signal in output cir 60 being directly coupled to the first color switching cuit 16 of signal separator 14 but there will be a second device 48 and being coupled to actuate the second sequen color signal provided in output circuit 8. Thus, after the tial switching device 50 through delay circuit 62 which delay provided by delay circuit 64, gate 54 will be opened delays the pulses provided by pulse generator 60 at a time at the time the first row of dots 83 has reached the print equal to the time required for a point on belt 22 to move ing head 38. The pulses provided by pulse generator 60 in the direction shown by the arrows 34 from the first as delayed by delay circuit 62 will now sequentially con printing heads 36 to the second printing heads 38; this nect the 7th through 11th electrodes 49 of printing head time delay is necessary in order to provide registry of the 38 to battery 58, and thus, since gate 54 is open during two-color information printed on the belt 22. Gate 52 60 this period due to the presence of the second color signal, is directly connected to output circuit 16 of signal sep incremental charges in dot form will be provided on belt arator 14 and thus will be actuated in the presence of 22. After these charges pass red toner applicators 68, the first color signal. Gate 54 is coupled to output circuit the red toner material will adhere to the incrementally 18 of signal separator 14 by delay circuit 64 providing charged areas providing the row of red dots 90, which the same time delay as delay circuit 62, and thus gate 54 may form the first line of the letter “O,” indicated at 89, is actuated responsive to the presence of the delayed sec these red dots being formed on the inner surface of belt ond color signal. Assuming then that the first color signal 22, but being visible therethrough. It will be readily com is present in the output circuit i6 of signal separating prehended that the red toner materia? provided by the red circuit 14 thereby actuating gate 52, each successive pulse toner applicator 68 will also adhere to the incrementally provided by pulse generator 60 results in sequential 70 charged areas provided by the first printing head 36, how connection of the next successive electrode 40 of printing ever, the black toner material applied by the black toner head 36 to battery 56 thereby pulsing dielectric belt 22 applicator 66 is opaque, and since it is applied on the outer successively to form incremetal charges in dot form surface of the belt 22, the red toner material applied on thereon. The action of the second color dot 46 the other surface, e.g., on the reverse side of belt 22 from is identical. 75 dots 83 will not be visible. 3,069,681 5 6 In order to erase the information “printed” on belt 22, Zontal and vertical deflection voltages, thereby positioning a pair of suitable erasing heads 92 are provided cooperat the beam from 10 to the proper ing with run 28 of belt 22 and spaced from the first color location on target 138 for the particular character called printing heads 36 in the direction opposite from the direc for by the digital code. In order to provide the raster tion of movement 34 of belt. 22. Erase heads 92 apply 5 scanning of the particular character, sweep generators a charge on the belt 22 having a polarity opposite from 125 are provided coupled respectively to horizontal and the incremental charges forming the dots and thus the belt vertical bean deflection elements 112 and 14 of tube is discharged and the toner material which is adhered to 166 and providing a delta x-delta y sweep voltage respec the incrementally charged areas is brushed therefrem. It tively superimposed on the position voltages provided by will be observed that while the previous page of informa O character selector 18. The delta x-delta y sweep voltages tion is being erased, the first color printing head 36 is provided by sweep generators 120 cause the electron beam operative to begin the application of a new electrostatic in tube 1:3 to be scanned over the particular character image of the first color on belt 22 to form a new page of selected in a television-type raster of sufficient size to two-color information. It will be seen that the belt may cover only the selected character on the target 108. The be stopped when a complete page of information appears 5 electron beam provided by electron guin 119 has a con in the viewing area 79, or in the alternative, motion of stant intensity and as it is scanned across the selected the belt may be continuous and information continuously character on the target, the current printed thereon and subsequently erased therefrom. It from the target is modulated since the aluminum target will also be readily apparent that it may be desirable to and the ink from which the characters are formed ex skew the printing heads 36 and 38 slightly in order that 20 hibit different secondary emission coefficients. Since the the dots printed thereby may appear horizontally on the target current is equal to the difference between the con viewing surface 70 of belt 22. As best seen in FiG. 2, an stant intensity bearin current and the varying secondary opaque front shield 92 may be provided having a viewing emission current, the character modulation appears across opening 94 therein which exposes only the display sur the output load 22. The character video signal face 70 of belt 22. While printing heads 36 and 38 are 25 in the output circuit 46 of character generator tube 106 shown as being formed of a single row of dot-forming is amplified by video 24 and applied to the electrodes, it will be readily apparent that each printing writing signal input circuit of electrical read-out storage head 36, 38 may be in the form of a dot matrix, contain turbe 326 by write-read-erase and prime control switch ing enough dots completely to form any of the required ?2?? characters or symbols. 30 Storage tube 126 is preferably a high resolution elec Referring now to FEG. 3 in which like elements are in trical output recording storage tube, such as Raytheon dicated by like reference numerals, have shown my type QK685. Storage tube 126 is necessary in the sys invention as embodied in a system of the type described term of FG. 3 since the system as thus far described is and illustrated in the aforesaid Hawkins' application, the capable of receiving digital input information at the rate illustrated system being intended for the large-area dis 35 of 30,000 characters per second, or 4,000 characters in play of alpha-numeric information. This system, gen 133 milliseconds, whereas ten seconds is required for erally identified as 09, comprises input unit 482 which visual display of 4,000 characters, thus a complete page provides the input information in digital form, i.e., a of information containing as many as 4,000 characters pulse code in which the character, position of the charac can be written into the storage electrode 130 of tube ter on the page, and the desired color are all included in 40 126 at a very fast rate and subsequently read-out at a the coded information. Digital input unit 62 may be a slower rate compatible with electrostatic printing appa computer, a teletype machine, or a device of the type ratus. Operation of the recording storage tube i 26 in manufactured by Frieden, Inc., referred to by the trade volves priming, writing, reading aid erasing. Priming is name “Flex-O-Writer.” Digital input unit C2 is cou accomplished by uniformly charging storage electrode pled to code identifier or decoding unit 04 which sep 130 by reducing the collector screen voltage below the arates the character identifying portion of the coded 45 critical potential and scanning the storage electrode 130 digital input from the position identifying portion and with an electron beam provided by gun 132 in raster the color identifying portion. The position identifying fashion. In the writing operation, the bias of control porton of the digital input code may merely indicate that grid 34 is set at cut-off and the signal to be stored is the system is to operate in a typewriter mode of opera applied. In the reading operation, the bias tion, i.e., letters printed from left to right, line after line 50 is set to permit beam current and the storage screen until a full page is completed; or it may identify a par voltage is adjusted so that the stored signal will modulate ticular location or locations on the page for particular the beam with the output then being taken from the characters or symbols. signal electrode portion of the storage electrode. Erasing Generation of time-based signals responsive respective operation is performed by writing a direct current signal ly to the input characters is accomplished by a character 55 into the tube, thus normalizing the storage electrode 130 generator tube G6, which in the illustrated embodiment at full modulation level with the signal electrode and may be a monoscope tube of the type manufactured by the storage screen voltage being the same. The mode Products Division, Hughes Aircraft Co. of operation of the electrical output storage tube is well In this tube, 64 characters and symbols (letters, numerais, known to those skilled in the art, and control of the punctuation, etc.) or more, are printed on aluminum 60 target 193 in ordinary printer's ink in horizontal and ver prime, write, read and erase functions is accomplished in tical rows. Tube 166 is provided with electron gun i.18 the ilustrated embodiment by switching unit 128. Code and horizontal and vertical deflection elements 12 and identifying unit 104 is coupled to the switching unit 128 E 4 which cooperate to scan the electron beam produced by connection 136 and thus provides a signal thereto at by the gun 13 over the target 4:3. The time-based out 65 the beginning of the input code group which initiates put signal corresponding to any preselected character is writing operation of the storage tube 126 which has provided in output circuit i6 of tube 66 by initially been previously primed as hereinafter described. positioning the electron beam on the desired character In the illustrated embodiment, code identifying unit and then scanning the character in raster fashion. in or 104 is coupled to grid 134 of storage tube 126 by con der to select the particular character and to position the 70 nection 133 in order to control the beam intensity during beam thereon, code identifying unit 24 is coupled to writing operation and thus the stored signal level respon character selector unit 118 which in turn is respectively sive to the color code. Thus, during writing operation, coupled to horizontal and vertical beam deflection ele characters which the code identifies as black are stored ments 112 and 14 of tube E06. Character selector i8 at one level and characters which the code identifies as thus converts the character code into corresponding hori 75 red are stored at a second level. The selected character 3,069,681 7 8 signals from the character generator tube 106 are written initiates operation of synchronous drive motor 32 to on the storage electrode 136 of the storage tube 26 at cause movement of the belt 22 in the direction shown positions determined by the position code, as identified by the arrows 33 when Switch 128 changes from writing by the code identifying unit 494. Code identifying unit to reading operation. 104 is coupled to character positioning unit 48 and if The output circuit 154 of storage tube 126 is coupled the input digital code indicates the typewriter mode of during reading operation by switch 128 to video amplifier operation, character positioner unit 40 will provide 156 and to signal separating means 44 which, in the illus horizontal and vertical "stair-step” beam deflection volt trated embodiment, comprises first and second signal clip ages for storage tube 26 which will sequentially posi ping circuits 158 and 469 which respectively separate the tion the beam provided by gun 132 from left to right O first and second color output signals as hereinbefore de and top to bottom. If, one the other hand, the input scribed. Thus, for example, the black information may be digital code calls for selective character positioning at Written into tube 126 at a level of four volts and the red in preselected locations on the page, character positioning formation may be written at a level of three volts. During unit 4te will provide the requisite vertical and horizontal read-out operation of the storage tube 26, the two-color beam positioning deflection voltages for the storage tabs 5 information is separated by clippers 58 and 160, clipper 126. Character positioning unit 149 is coupled to hori 58 being biased to pass all signals above 3.5 volts (back Zontal and vertical beam deflection elements 42 and 3&4 information), and clipper 166 being biased to pass all in of storage tube E26 by a sweep amplifier E46 and sweep formation above 2.5 volts (both black and red informa Selector switch 4S. Sweep selector switch 143 is actu ion), the two signals then being subtracted to provide ated by Switch i28 to connect beam defection elements 20 the red information alone. The first, or black color clip 142 and 144 of storage tube 126 to character positioning per 158 is thus coupled to the first color dot switch 44 unit 40 during writing operation and to other sweep while the second, or red, color clipper 169 is coupled to generating means during reading, erasing and priming the Second color dot Switch 46 by the signal delay circuit operations, as will be hereinafter described. The delta 64, the display and printing portion of the system of FIG. x-delta y Sweep generators 289 also are coupled to sweep 3 being as described in connection with FIGS. 1 and 2, 146, and it will thus be seen that the writing above. beam in storage tube 326 is initially positioned on the When dot Switch 44 has competed one sequential sam Storage electrode 30, at the proper position called for pling of the output signal from storage tube 130 thereby by the input digital code, and then swept in raster fashion providing one horizontal line scan of belt 22, a trigger to Write the selected character from the character gen 30 signal is provided to horizontal sweep generator 74 by a erator tube 66 onto the storage electrode 1382 at one connection 162 in order to initiate a new horizontal sweep of two levels selected by the code identifier 104 respon of the reading electron beam on the storage tube 126. Sive to the color code in the input digital code. It will Vertical sweep generator 76 which is synchronized with be seen that the horizontal and vertical saw-tooth or Synchronous drive motor 32 may be a simple potenti delta x-delta y writing sweeps of the electron beam of ometer which thereby provides the vertical sweep voltage Storage tube 26 provided by electron guin 32 are similar for the storage tube 54 in synchronism with drive motor in shape and identical in time to the character scanning 32 during the read-out operation. 76 may SWeeps of the character generator tube (6. also be coupled to Switch 128 by connection 64 thereby Assuming now the typewirter mode of operation, it will to provide an actuating signal thereto at the end of one be seen that after the first character has been completely 40 complete vertical scan of the storage electrode 30 of written into the storage electrode 13 of storage tube Storage tube 126 thereby to actuate switch 128 successively 126 at a level determined by the color code, character to erase, prime, and write operation. Control switch 128 positioner 40 will advance the line scanning sweep one may be coupled to the digital input unit 102 to provide horizontal step so that another character may be written a trigger signal thereto at the end of the vertical priming onto the storage electrode 39. This continues sequen scan of the storage tube 126, thereby indicating that the tially until the complete horizontal line has been written complete page of stored information has been read out on the storage electrode 130, at which point the hori of the storage tube and displayed and thus that a new Zontal line scanning is returned to its starting point and page of input information may be read into the character the vertical page scanning sweep is advanced one step generator tube 106. downward. The page scanning continues to advance 50 It will be seen that actuation of the switch 128 from one line at a time after each horizontal line is completed reading to erase and priming operation will, by virtue of until the page is finished. The end of the page is indi connection 129, turn off pulse generator 60 and the syn cated in the input digital code, and thus code identifying chronous drive motor 32, thus terminating operation of unit 164 will provide a signal to switch 123 and to char dot switches 44 and 46, horizontal sweep generator 74 acter positioner 149 indicating the end of the page so that 5 5 and the dielectric display belt 22. Actuation of control the writing beam of the storage tube 126 is blanked Switch 23 from read-out to erase and prime likewise off, sweep selector switch 28 is actuated to switch from changes switch 148 from reading to erase and prime oper writing to reading operation, and storage tube 126 is ations, thereby connecting deflection means 142 and 144 changed from writing to reading operation. of storage tube 26 to erase and prime SWeep generators Read-out of the stored data on the storage electrode 60 and amplifiers 145 in order to prepare the storage tube for 130 of storage tube 26 is accomplished by scanning Writing the next page of information onto the storage elec the storage electrode 3 with the electron beam from trode 530. On completion of the priming operation, electron gun i32 with a television-type raster large enough erase and prime sweep generators and amplifiers 67 actu to cover the entire page of stored information. Linear ate Switch 128 thereby in turn actuating switch 48 con saw-tooth sweep voltages are employed for both the necting deflection means 42 and 144 of storage tube 126 horizontal and vertical scans, the horizontal sweep volt to character positioner 148 and sweep generators 120 in ages during reading operation being provided by hori order to Write the next page of information onto the stor Zontal sweep generator 74 and the vertical saw-tooth age electrode 33. voltage being provided by the vertical sweep generator Referring now to FIG. 4, there is shown the preferred 76. Horizontal and vertical sweep generators 4 and 70 embodiment of dot switch 44, it being understood that dot 76 are coupled to the horizontal and vertical deflecticin Switch 46 is identical. in the specific embodiment shown, elements 142 and 44 of storage tube 126 during read Writing head 36 associated with dot switch 44 provides ing operation by sweep selector switch 343 and sweep 1,024 individual dots equally spaced apart in a straight amplifiers 150. The switch 128 is connected to the syn horizontal line across the width of the dielecetric belt chronous drive motor 32 by a connection. E52 and thus 22. These dots must be sequentially turned on and off 3,069,681 9 10 from left to right across the display at the rate of 256,000 40-2, etc. The thirty-two output circuits 216 of dots per second to provide a horizontal sweep rate of matrix 214 are respectively coupled to the thirty-two 250 lines per second. During the time of each sequential electrodes 42 by gate tubes 52. Each of the gate tubes actuation of the 1,024 dots, the dielectric material belt 52 has its plate 218 coupled to a suitable source 222 of 22 is moved vertically in the direction 34 (FIG. 1) at positive plate potential by plate resistor 224 and to the a constant rate by drive motor 32 so that each successive respective electrode 42. The control grid 226 of each line is printed just below its predecessor, much in the of the gate tubes 52 is coupled to the respective output manner of a television raster. circuit 216 of the diode switching matrix 214, and the In order to accomplish the successive sequential switch cathode 228 is connected to ground by cathode resistor ing of the 1,024 individual printing elements, pulse gen O 230. All of the cathodes 228 of the thirty-two gate tubes erator 60 is a stable 256 kc. pulse generator, i.e., it pro 52 are connected to the output circuit 16 of the first color vides 256,000 timing pulses per second. The output cir clipper 158 (the cathodes of the gate tubes 52 of the cuit 166 of pulse generator 60 is coupled to the input of a other dot switch 46 are coupled to delay circuit 64). five-stage binary counter 168 formed of five bistable multi It will now be seen that the video information from vibrators 170, 172, 174, 176 and 178. Binary counter 5 the storage tube 126, as separated into its two-color com 168 is in turn coupled to a diode switchi unatrix 80 ponents by the clipping circuits 158 and 160, is coupled which employs ninety-six sequentially to pulse 32 to the cathodes 226 of the gate tubes 52 of the two dot output circuits on and off. The five stage binary counter switches 44 and 46 during writing operation. Referring 168 and diode switching matrix 180 do not form a part of to the first color dot switch 44, when a black mark is to my invention, per se, being shown and described in the 20 be printed on the dielectric belt 22, the video information Proceedings of the Institute of Radio Engineers, volume applied to the cathodes 228 is negative and therefore the 37, February 1949, pages 139-147. respective tube 52 is keyed on by the positive-going pulse Electrodes 40 of writing head 36 comprise 1,024 indi applied to the respective grid 226 from the respective vidual dot forming electrodes divided into thirty-two output circuit 26 of the diode matrix 214 so that the groups of thirty-two electrodes. The electrodes of each 25 respective tube 52 conducts heavily, thereby applying to group of electrodes 40 are respectively connected in paral belt 22 a negative pulse with respect to the pulses applied lel, as shown, i.e., electrodes #1 of all of the thirty-two by the electrodes 40. When, on the other hand, a black groups are connected in parallel, electrodes #2 of all of mark is not to be printed, the video signal in output cir the thirty-two groups are connected in parallel, etc. cuit 16 from the first clipper 158 is essentially zero and It will be seen that the counter 168 and diode switching 30 therefore the respective tube 52 will not be gated on, matrix 180 provides a pulse output sequentially on each even in the presence of a positive pulse applied to its of the thirty-two output circuits 182 of switching matrix grid 226 from the respective output circuit 216 of the 180, i.e., the first pulse received from pulse generator 6) diode switching matrix 214. in essence appears on the first output circuit 182-1 of As previously indicated, pulse generator 60 is coupled matrix 180, the second pulse of the pulse generator 60 35 to horizontal sweep generator 74 in order to initiate the appears on the second output circuit 132-2, etc. The horizontal scanning sweep supplied to horizontal deflec thirty-two output circuits 182 of the diode switching tion element 142 of storage tube 126 during read-out op matrix 180 are respectively connected to the thirty-two eration, and the final output of binary counter 212 is also parallel connected electrodes 40 of writing head 36 by applied to horizontal sweep generator 74 in order to ini pulse 184 which provide the desired posi tiate a new horizontal sweep responsive to completion of tive voltage pulses on the electrodes 46. Thus, output the pulse count of 1,024. circuit 182-1 from the switching matrix i80 is coupied It will be understood that the system shown in FIG. 3 to base 186 of 190-1 which has its emitter and the counting and switching apparatus shown in FIG. 192 connected to ground, and its collector 194 coupled to 4 are not my invention, per se, but form a part of my one end of primary winding 196 of 184-1. 45 improved two-color large area display system. The other end of primary winding 196 is connected to a While I have described above the principles of my in suitable source 198 of positive potential by diode 200, and vention in connection with specific apparatus, it is to be another diode 202 is coupled across primary winding clearly understood that this description is made only by 196 of transformer 184-1. Secondary winding 204 of way of example and not as a limitation to the scope of transformer 184-1 has one end connected to a suitable 50 my invention. source 206 of positive potential and has resistor 208 con What is claimed is: nected thereacross. The other side of secondary winding 1. A system for large area display of information in 204 is connected to the number one electrode of each of two colors comprising: means for receiving said informa the thirty-two groups of electrodes 40. The other output tion and for converting the same into two time-based sig circuits 182 of the diode switching matrix 180 are similarly 55 nals respectively responsive to the information in said connected to the respective electrodes 40 by two colors; a relatively thin sheet of transparent dielectric 190-2, 190-3 and pulse transformers 184-2 and material; means including a first plurality of electrodes 184-3, as shown. Positive going pulses are thus sequen in spaced apart alignment along one dimension of Said tially applied to the thirty-two electrodes 40 of all of the sheet and cooperating therewith to form first incremental groups of electrodes, these pulses being of such amplitude 60 electrostatic charges thereon in dot form when said first that the dielectric belt 22 will be incrementally charged electrodes are respectively pulsed; means including a Sec in dot form when a negative pulse of suitable amplitude is ond plurality of electrodes in spaced apart alignment applied to the opposite side of the belt by the other elec along said one dimension of said sheet and cooperating trodes 42. therewith to form second incremental electrostatic charges The final output of the binary counter 168 which is 65 thereon in dot form when said second electrodes are re an 8 kc. pulse train in line 210 is coupled to the input spectively pulsed, said second plurality of electrodes being of another binary counter 212 and diode switching matrix spaced from said first plurality along the other dimen 24, identical respectively to counter 168 and diode matrix sion of said sheet; means for moving said sheet with re 180. Electrodes 42 on the other side of belt 22 from spect to said first and second electrodes along said other electrodes 40 comprise thirty-two electrodes respectively 70 dimension; first switching means sequentially coupling said associated with the thirty-two groups of thirty-two elec first electrodes to said converting means for sampling one trodes 40. Thus, the first electrode 42-1 cooperates with of said signals at discrete intervals and for pulsing Said the thirty-two electrodes of the first group of electrodes first electrodes responsive to the presence of Said one 40-1, the second electrode 42-2 cooperates with the signal at the respective intervals; second switching means thirty-two electrodes of the second group of electrodes 75 sequentially coupling said second electrodes to said con

3,069,681 3 : 4. means having the same delay as said first-named delay intensity control means, a storage electrode, a writing means and coupling said pulse generating means to the signal input circuit, an output circuit, and beam deflecting connecting means of said second switching means; said means; means coupled to said storage tube for selectively pulse generating means being coupled to said horizontal changing the same from writing to reading operation, sweep generating means for synchronizing the same; said said changing means coupling said character generator moving means being coupled to said vertical sweep gen means to said writing signal input circuit, coupling said erating means for synchronizing the same; first means for positional signal generating means to said deflecting means, applying charged toner material of one color to one side and said color signal generating means to said beam in of said sheet following said first electrodes; second means tensity control means during writing operation thereby im for applying charged toner material of the other coicr 0. pressing said character signal on said storage electrode to the other side of said sheet following said second elec at locations responsive to said position signals and at trodes; and means cooperating with said sheet for erasing levels responsive to said color signals; said changing means said charged toner material therefrom. coupling said horizontal and vertical sweep generating 9. The combination of claim 8 wherein said informa means to said deflecting means during reading operation tion is alpha-numeric in form and coded as to character, for scanning said beam over said storage electrode thereby position, and color; and in which said receiving and con to provide said first time-based signal in said output cir verting means comprises code identifying means for re cuit having two levels respectively responsive to said color ceiving the coded information and for separating the char code; said output circuit being coupled to said separating acter, position and color codes; character generator means means; and in which said separating means comprises two coupled to said code identifying means for providing char 20 clipping means for respectively clipping said first signal to acter signals responsive to the character code; means cou provide said second and third signals respectively respon pled to said code identifying means for generating posi sive to said two levels. tion signals responsive to the position code; means coupled to Said code identifying means for generating first and References Cited in the file of this patent second color signals responsive to the color code; a signal 25 UNITED STATES PATENTS to-signal storage tube having beam producing means, beam 2,752,833 Jacob ------July 3, 1956